Update citation information CITATION.cff and BibTeX in README

Author: seisman

CITATION.cff

@@ -76,9 +76,9 @@ authors:
   family-names: Wessel
   affiliation: University of Hawaiʻi at Mānoa, USA
   orcid: https://orcid.org/0000-0001-5708-7336
-date-released: 2025-10-03
-doi: 10.5281/zenodo.17156962
+date-released: 2026-01-06
+doi: 10.5281/zenodo.18080259
 license: BSD-3-Clause
 repository-code: https://github.com/GenericMappingTools/pygmt
 type: software
-version: 0.17.0
+version: 0.18.0

README.md

@@ -137,7 +137,7 @@ Feel free to cite our work in your research using the following BibTeX:
 
 ```
 @software{
-  pygmt_2025_17156962,
+  pygmt_2026_18080259,
   author       = {Tian, Dongdong and
                   Leong, Wei Ji and
                   Fröhlich, Yvonne and
@@ -157,12 +157,12 @@ Feel free to cite our work in your research using the following BibTeX:
                   Uieda, Leonardo and
                   Wessel, Paul},
   title        = {{PyGMT: A Python interface for the Generic Mapping Tools}},
-  month        = oct,
-  year         = 2025,
+  month        = jan,
+  year         = 2026,
   publisher    = {Zenodo},
-  version      = {0.17.0},
-  doi          = {10.5281/zenodo.17156962},
-  url          = {https://doi.org/10.5281/zenodo.17156962}
+  version      = {0.18.0},
+  doi          = {10.5281/zenodo.18080259},
+  url          = {https://doi.org/10.5281/zenodo.18080259}
 }
 ```